A potable water system can be installed in an aircraft to supply cabin outlet facilities (e.g., handwash basins in lavatories and sinks in onboard kitchens) with fresh water. A potable water system can comprise a water storage tank, a supply line and tap lines which connect the water supply tank to the outlet facilities. A purification device is located within the potable water system so as to optimize its purification purposes while also being compatible with installation, inspection and maintenance.